Optical beamsplitters are known. Some beamsplitters are made by cementing two prisms together with a reflective film in between. See e.g. U.S. Pat. No. 7,329,006 (Aastuen et al.) Lenses are also known. Known lenses include compound lenses in which two or more simple lenses are cemented together. U.S. Pat. No. 5,654,827 (Reichert) discusses lenses in which the lens is divided into two parts by a beamsplitter.
Head-Up Displays or Head-Mounted Displays (collectively referred to herein as HUDs) can project an image that fills all or part of a user's field of view. Some HUDs use a combiner optic that integrates the projected image with the usual image of the external environment. In some cases, the HUD is a Near-Eye Display (NED), which may have a form factor similar to that of eyeglasses. See e.g. U.S. Pat. No. 6,353,503 (Spitzer et al.).